docs: def setup(config):
      """Setup persistence to be used in cinderlib.
  
      By default memory persistance will be used, but there are other mechanisms
      available and other ways to use custom mechanisms:
  
      - Persistence plugins: Plugin mechanism uses Python entrypoints under
        namespace cinderlib.persistence.storage, and cinderlib comes with 3
        different mechanisms, "memory", "dbms", and "memory_dbms".  To use any of
        these one must pass the string name in the storage parameter and any
        other configuration as keyword arguments.
      - Passing a class that inherits from PersistenceDriverBase as storage
        parameter and initialization parameters as keyword arguments.
      - Passing an instance that inherits from PersistenceDriverBase as storage
        parameter.
      """
      if config is None:
          config = {}
      else:
          config = config.copy()
  
      # Prevent driver dynamic loading clearing configuration options
      volume_cmd.CONF._ConfigOpts__cache = MyDict()
  
      # Default configuration is using memory storage
      storage = config.pop('storage', None) or DEFAULT_STORAGE
      if isinstance(storage, base.PersistenceDriverBase):
          return storage
  
      if inspect.isclass(storage) and issubclass(storage,
                                                 base.PersistenceDriverBase):
          return storage(**config)
  
      if not isinstance(storage, six.string_types):
          raise exception.InvalidPersistence(storage)
  
      persistence_driver = driver.DriverManager(
          namespace='cinderlib.persistence.storage',
          name=storage,
          invoke_on_load=True,
          invoke_kwds=config,
      )
      return persistence_driver.driver